Leptomycin A

A strain of Streptomyces was found to produce new antifungal antibiotics. The active compounds were purified and separated into two substances named leptomycin A and B by high performance liquid chromatography. The molecular formulae of leptomycins A and B are C32H46O6 and C33H48O6 respectively, and physicochemical and biological properties of them are very similar to each other. Leptomycins A and B exhibit strong inhibitory activity against Schizosaccharomyces and Mucor.

Leptomycin exerts its antifungal and anti-tumoral activity via inhibiting nucleo-cytoplasmic translocations in eukaryotic cells. To learn more about the biosynthesis of leptomycin and in an effort to generate leptomycin analogues through genetic engineering, 90 kb segment of DNA containing the putative leptomycin (lep) biosynthesis cluster from Streptomyces sp. ATCC 39366 was cloned and sequenced. The lep cluster consist of 12 polyketide synthase (PKS) modules distributed in four genes (lepA, B, C and D) and a P450 encoding gene. The lep gene cluster was confirmed by its successful expression in Streptomyces lividans, where it directed the production of the two natural congeners-leptomycins A and B. The production of leptomycin B showed that the host has the capability to synthesize ethylmalonyl-CoA.

Basal stem rot (BSR), orGanodermarot disease, is the most serious disease associated with the oil palm plant of Southeast Asian countries. A basidiomycetous fungus,Ganoderma boninense, is the causative microbe of this disease. To control BSR in oil palm plantations, biological control agents are gaining attention as a major alternative to chemical fungicides. In the course of searching for effective actinomycetes as potential biological control agents for BSR,Streptomyces palmaeCMU-AB204Twas isolated from oil palm rhizosphere soil collected on the campus of Chiang Mai University. The culture broth of this strain showed significant antimicrobial activities against several bacteria and phytopathogenic fungi includingG. boninense. Antifungal and antibacterial compounds were isolated by antimicrobial activity-guided purification using chromatographic methods. Their structures were elucidated by spectroscopic techniques, including Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), Ultraviolet (UV), and Infrared (IR) analyses. The current study isolated new phenyl alkenoic acids1-6and three known compounds, anguinomycin A (7), leptomycin A (8), and actinopyrone A (9) as antimicrobial agents. Compounds1and2displayed broad antifungal activity, though they did not show antibacterial activity. Compounds3and4revealed a strong antibacterial activity against both Gram-positive and Gram-negative bacteria including the phytopathogenic strainXanthomonas campestrispv.oryzae. Compounds7-9displayed antifungal activity againstGanoderma. Thus, the antifungal compounds obtained in this study may play a role in protecting oil palm plants fromGanodermainfection with the strainS. palmaeCMU-AB204T.